Demons of the Rich and Famous (Demon Whisperer book 1)

During a year-long coma--literally spent in hell--seventeen-year-old Caden Butcher developed a special power. He can speak to demons in their own language. Awakening with this new ability, Caden takes over the family exorcism business and becomes known as the young whiz-kid exorcist to the stars, obtaining most of his work from Hollywood. But what others don't know is the exorcisms are all staged with the help of his best buddy, Dantalion, a demon he met in while he was in hell.
When an exorcism goes wrong, Caden discovers the demon inside a teen girl is not your normal malicious entity, but an adversary from down under who is hell-bent on Caden's destruction because of what Caden did to him while in hell.
Now with the help of Dantalion and Caden's girlfriend Aspen, a skilled necromancer, Caden must track down the rogue demon before he can expose Caden as a fraud and end his reign as the one and only Demon Whisperer.